The present invention relates generally to equipment utilized in conjunction with subterranean wells and, in an embodiment described herein, more particularly provides a downhole electrical power system.
There are many uses for a downhole electrical power system. These uses include providing power to operate well tools, such as sensors, data storage devices, flow control devices, transmitters, receivers, etc.
Unfortunately, the downhole environment is frequently inhospitable to some types of power systems. For example, batteries typically cannot withstand wellbore temperatures for long.
Other types of power systems generate electrical power from fluid flow in a well. For example, turbines have been used to drive generators in order to produce electrical power downhole. However, these power systems cannot provide electrical power when the fluid flow ceases.
Therefore, it may be seen that a need exists for an improved downhole electrical power system. Preferably, the improved downhole electrical power system will be able to withstand the downhole environment and will not rely on fluid flow to generate its electrical power.
In carrying out the principles of the present invention, in accordance with an embodiment thereof, a downhole electrical power system is provided which satisfies the above need in the art. The power system utilizes a voltaic cell to provide electrical power to a well tool downhole.
In one aspect of the invention, a downhole electrical power system includes an electrical power-consuming well tool interconnected in a tubular string. A power source provides the well tool with electrical power and includes at least one voltaic cell. The voltaic cell has an electrolyte which may be isolated from well fluid, or the electrolyte may be well fluid.
A first barrier, such as a floating piston, may be used to isolate the electrolyte from the well fluid. An insulating fluid may be disposed between the well fluid and the electrolyte, and another barrier may be used to isolate the insulating fluid from the electrolyte. One or both of these barriers may be permeable to hydrogen gas generated in the voltaic cell. The barriers may transmit fluid pressure, so that the electrolyte is at substantially the same pressure as the well fluid.
These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of a representative embodiment of the invention hereinbelow and the accompanying drawings.